This invention relates to detecting and separating objects and more particularly to a system and method for detecting or sensing the adequacy of a lining or color on a work piece in a high speed industrial process and removing work pieces that have an inadequate lining or color.
Metal closures for plastic and glass containers are well-known and popular for packaging food and other products. A conventional metal closure for a packaging container often is a screw closure of the kind having a peripheral skirt with an internal lining of a compound. Either after forming or upon assembly of the closure to the neck of a container, the closure internal lining is capable of permanently or semi-permanently conforming to screw thread formations on the container neck or to the container neck or rim. Thus, the lining may form or enhance sealing between the closure and the container such that the container may contain a negative pressure or vacuum therein, which is typically formed during the product filling process. As an example of a lining in this regard, a plastisol compound may be sprayed onto the inside surface of the closure panel, after which the closure having the plastisol may be heat cured before coupling the closure to the container. The lining preferably is substantially deformable such that the lining forms or enhances sealing between the closure and the container neck and/or rim.
A particular type of closure that is suitable for a container having an internal vacuum may be first fitted on the container by the beverage or food manufacturer by a simple pressing and/or twisting action. The closure subsequently may be repeatably removed by the consumer using a conventional twisting action. Such closures are often referred to as “press-twist” closures. Press twist and other vacuum closures are often used for products that are either hot-filled or are thermally pasteurized or sterilized after filling and closing, such as baby food products, preserves, and the like.
Press twist closures often are provided with tamper-evident buttons at the center of their closure panels, which overlie the mouth of the container to which they are fitted. A typical button is an integral, raised circular part of the closure panel, which is held in an inverted, depressed position by the vacuum within the container, but which returns resiliently to its raised position if the vacuum is for any reason subsequently broken or substantially reduced. The button thus indicates, for example, whether the integrity of the seal between the container and the closure has been maintained, or the closure has not made a proper seal with the container. A button disposed in its raised position before an initial opening by an end user may indicate that the product contents of the container may be degraded or spoiled.
Other closures are of the “roll-on” type, which describes the manner in which the skirt is formed with screw threads after the closure has been applied to the container. Roll-on closures are used extensively for liquid products such as fruit cordials and squashes, spirits and mineral waters, which are typically filled cold, and normally do not require heat treating after filling and closing. Roll-on type closures also form a seal between the closure and the container in order to enhance preservation and freshness of the contents of the container, and to maintain an internal negative pressure or vacuum within the container until the initial opening of the closure by an end user.
The closure lining process typically is a high-speed, automated process in which an uncured plastisol or similar compound is sprayed onto an inside surface of a panel of the closure. Typical through-puts on a belt conveyor or other conventional conveyor may be, for example, 300 to 800 closures per minute, although rates of 2500 closures per minute or more may also be achieved. Inherent in such a high-speed lining coating or spray process, some of the closures produced by such a process will have a lining that is discontinuous or missing, or otherwise falling outside of specified values or tolerances. For example, one of a series of spray nozzles may become clogged, the supply of compound material may become interrupted such that spray is interrupted, a closure may be misaligned with a spray nozzle, or like spraying failures may cause one or a series of closures to be moved from a compound station even though it lacks an appropriate lining.
The problem of a deficient or missing lining is exacerbated because a closure having a deficient or missing lining may produce a disproportionately large economic impact in that the deficient or missing lining is often detected only after filling of a product in the container. Specifically, after a container has been filled with product, a pressure or tamper-evident button on the closure may indicate that the seal between the closure and the container is not air tight. In circumstances in which a deficient closure panel lining is the cause of the insufficient seal, the failure of the seal may cause the entire container and contents to be discarded. Conventional inspection methods generally have been insufficient to fully alleviate this problem.